The time dependence of the intracranial blood pressure and the cerebrovascular pulsatility are essential parameters for the autoregulation of brain blood circulation. The time dependencies of these parameters, such as the shape of the intracranial pressure pulses and their reactions to various tests (jugular veins compression, hyperventilation, retention or respiration, various pharmacological tests, etc.) indicate accurately the type of pathology. For that reason, in vivo dynamic intracranial blood pressure measurements are made in clinical practice.
But known measurement methods for that purpose are invasive. That means, it is imperative to trapan the human crane and implant a mechanical/electrical sensor for pressure measurement, see for example publications on these techniques: Richards R., Illingworth R., "A Single System of Intracranial Pressure Monitoring for Use by Non-Neurosurgeons", Intensive Care Med. 12 (1986), 325-327; Mohsenipour I., "Modified Epidural Measurement of the Intracranial Pressure", Zentralblatt for Neurochirurgie (VEB Johann) 50 (1989), 24-27.
Non-invasive ultrasonic Doppler blood velocity meters are known and used for diagnosing intracranial basal arteries, see U.S. Pat. No. 4,930,513, Jul. 26, 1990, entitled "Two Dimensional Processing of Pulsed Doppler Signals". Methods of ultrasound echoscopy are known. For example, in "Physical Principles of Medical Ultrasonics", Editor C. R. Hill, Ellis Horwood LEd. Publishers: A Division of John Wiley & Sons (1986), an ultrasonic technique is described for the production of images of structures within a body corresponding to a local value of ultrasound attenuation at a corresponding point in the body. These methods have recently been described in U.S. Pat. No. 4,389,892 to Jonathan Ophir and Nabil Maklad and in U.S. Pat. No. 4,676,250 to Casper W. Barnes.
However, ultrasonic Doppler or echoscopic methods do not allow one to get information on dynamic characteristics of cerebrovascular pulsations of a human intracranial medium such as their time dependencies.